Low alloy steel of high mechanical strength, little sensitive to quenching, weldable, etc.



Patented Aug. 28, 1951 LOW ALLOY STEEL OF HIGH MECHANI- CAL STRENGTH, LITTLE SENSITITE TO QUENCHING, WELDABLE, ETC.

Vittorio De Gaspari and Aldo Bartocci, Terni,

Italy, assignors to Terni societa per lIndustria e lElettricita, Terni, Italy, a company of Italy No Drawing. Application March 29, 1949, Serial i 4 Claims.

This invention relates to a low-alloy-steel, possessing high mechanical characteristics and such, that, in virtue of its chemical composition, it manifests a limited variation of the mechanical-strength, in the various phases of the heat treatment: rough shaping in the warm state, state of normalization, state of quenching.

In all these conditions, the high mechanical strength is accompanied by the relatively high values of elongation, shrinkage and resilience.

In the annealed state also the mechanical strength is high, though remarkably inferior to the one relative to the states above mentioned. In association with said characteristics the steel possesses satisfactory properties of weldability whilst in the quenching it manifests dangers of fracture, by far inferior to those of the standard hardened and tempered steels.

The prerogatives above mentioned are suitable for being drawn advantage from, in the manufacture of railway-tires or other elements, to obtain a product having a resistance to wear higher than that of the common tires and not liable to becoming fragile nor cracked in consequence of local hardening which might be brought about while the brakes are being put on: in some cases the tire can be made use of, even in the mere rolled state, obtaining thus a cycle of manufacture, both economical and quick. gether analogous field, this steel is apt of being used for the production of rails; now, in such application, apart from the high resistance to wear, there will prove very useful also the satisfactory characteristics of weldability.

In the field of profiled goods also, this steel can enjo a large application by obtaining profiled goods possessing high mechanical strength and elevated toughness, to be used for welded or riv eted structures in accordance with the project and the degree of weldability deriving from the particular chemical composition, which has been adopted. Analogous field of application is to be found in the round irons for reinforced concrete and in the rivets.

In the field of sheets and plates, the possibilities of application, in which are comprised also the naval, motor car and aircraft constructions, embrace a larger range, there being provided both the normalizing and alloying treatments: in order to obtain the highest mechanical strength associated with the elevated toughness, the hardening and tempering should be carried out with tempering at low temperature. The steel may be also used in the manufacture of electrodes for welding, by which weldings are obtained having In an alto- No. 84,248. In Italy April 8, 1948 a high strength with features analogous to those of the basic material dealt with in the present application.

The range of mechanical strength, which can Tensile State strength Kg/mmq. Roughly shaped in the Warm state -140 Normalized 90-140 Qucn chad 1l0-160 These high figures of the tensile strength are accompanied by relatively elevated resilience values.

The chemical composition of the steel, subject matter of this invention, may vary in between somewhat large limits, in accordance with the mechanical characteristics to be obtained, in relation to the more or less good characteristics of weldability desired, and in relationship to the sizes of the objects to be manufactured.

The chemical composition provides, apart from a somewhat low carbon content, for the presence of various specific elements, in not very high ratios, and substantially: silicon, manganese, nickel, chromium, with eventual additions. in still not very high ratios, of molybdenum, vanadium, and copper.

As a rule, the chemical composition is characterised by the following ratios of the said specific elements:

Carbon 0.14-0.26 Silicon 0.50-1.50 Manganese 0.80-1.50 Nickel 0.80-1.80 Chromium 0.501.50 Molybdenum 0.30 Vanadium 0. 5 Copper 0.80

An example of particular chemical composition in the case of a steel of a not very enhanced resistance (tensile-strength comprised within the range of 90 to Kg/mmq. in the normalized state) but having a good weldability, is the following:

Carbon 0.14-0.17 Silicon 0.80-1.00 Manganese 100-1.20 Nickel l.00-1.20 Chromium 0.80-1.00 Molybdenum 0.15-0.20 Vanadium 0.10-0.15 Copper 0.30-0.50

For an analogous range of mechanical strength, though with a somewhat inferior but rather satisfactory weldability, an example for a chemically economical composition, is given hereunder:

Carbon 0.17-0.21 Silicon 1.00-1.30 Manganese 1.10-1.30 Nickel 1.10-1.30 Chromium 0.90-1.10

An example of chemical composition suitable for the embodiment of higher strength values (tensile strength between 110 and 140 Kgr/mmq.

in the normalized state) but with a good weldability, is given hereunder:

Carbon 0.16-0.22 Silicon 100-1.30 Manganese 1.10-1.30 Nickel 1.20-1.40 Chromium 0.90-1.10 Molybdenum 0.20-0.30 Vanadium 0.10-0.20

Concerning an analogous range of strength, with a somewhat inferior, but still satisfactory weldability, an example of a more economical chemical composition, is given hereunder:

Carbon 0.19-0.25 Silicon 1.00-1.30 Manganese 1.10-1.40 Nickel 1.20-1.60 Chromium 0.90-1.20

Carbon 0.14-0.17 Silicon 0.80-1.00 Manganese e 100-1.20 Nickel 100-1.20 Chromium 0.80-1.00

With this steel one can obtain, in the normalized state, figures of tensile strength, comprise within the range of 80 to 100 Kg/mmq.

Still another example of chemical composition for still lower resistances is given by the following one:

Carbon 0.14-0.17 Silicon 0.50-0.80 Manganese 0.80-l.00 Nickel 0.80-1.00 Chromium 0.80-1.00 Copper 0.40-0.70

to which in the normalized state, belong figures of tensile strength comprised in the range of to Kg/mmq.

We claim:

1. A weldable steel of high tensile strength, which consists essentially of, in addition to iron, 0.14-0.26% carbon, 0.50-1.50% silicon, 0.80-l.50% manganese, 0.80-l.80% nickel, 0.50-1.50% chromium, and at least one of the following elements in the specified proportions, up to 0.30% molybdenum, up to 0.25% vanadium, and up to 0.80%

copper.

2. A weldable steel characterized by a tensile strength of 60 to kilograms per square millimeter, which consists essentially of, in addition to iron, 0.14-0.17% carbon, 0.50-0.80% silicon, 0.80-1.00% manganese, 0.80-1.00% nickel, 0.80- 1.00% chromium, GAO-0.70% copper.

3. A weldable steel characterized by a tensile strength of 110 to 140 kilograms per square millimeter, which consists essentially of, in addition to iron, 0.164122% carbon, -1.30% silicon, -1.30% manganese, 1.20-1.40% nickel, 0.90- 1.10% chromium, 0.20-0.30% molybdenum, 0.10- 0.20% vanadium.

4. A weldable steel characterized by a tensile strength of 90 to 110 kilograms per square millimeter, which consists essentially of, in addition to iron, 0.14-0.17 carbon, 0.80-1.00% silicon, 100-1.20% manganese, 100-1.20% nickel, 0.80- 1.00% chromium, 0.15-0.20% molybdenum, 0.10- 0.15% vanadium, 0.30-0.50% copper.

VITTORIO DE GASPARI. ALDO- BARTOCCI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1.917.527 Klinkenberg July 11, 1933 FOREIGN PATENTS Number Country Date 48,421 France Feb. 3, 1938 (Addition to No. 820,827)

83,074 Austria Apr. 15, 1919 461,251 Great Britain Feb. 10, 1937 666,251 Germany Sept. 27, 1938 739,424 France Jan. 12, 1933 

1. A WELDABLE STEEL OF HIGH TENSILE STRENGHT, WHICH CONSISTS ESSENTIALLY OF, IN ADDITION TO IRON, 0.14-0.26% CARBON, 0.50-1,50% SILICON, 0.80-1.50% MANGANESE, 0.80-1.80% NICKEL, 0.50-1.50% CHROMIUM, AND AT LEAST ONE OF THE FOLLOWING ELEMENTS IN THE SPECIFIED PROPORTIONS, UP TO 0.30% MOLYBDENUM, UP TO 0.25% VANADIUM, AND UP TO 0.80% COPPER. 